P1260: BIODISTRIBUTION OF LABELED AUTOLOGOUS AND ALLOGENEIC BONE MARROW MESENCHYMAL STROMAL CELLS IN RABBITS AFTER INTRAVENOUS ADMINISTRATION
Authors: Anastasiya Pestrikova, Elena Poponina, Elena Perfilova, Maria Sarpova, Elena Kalinina, Aleksandr Kardovskij, Anastasiya Endakova, Natalia Glubokovskikh
Journal: HemaSphere (2023)

Topic: 21. Stem cell transplantation - Experimental Background: Mesenchymal stromal cells (MSC) are used for cell therapy. This type of cells has the ability to immunomodulate and migrate to inflamed tissue areas. Studies of the biodistribution of MSCs in animals have shown equivocal results. Depending on the route of administration and the source of origin, MSCs are mainly found in the lungs, liver and other organs, but also in inflammatory foci. Fluorescent dyes can be used to study the pharmacokinetics of MSCs. Carboxyfluorescein succinimidyl ether (CFSE) stably binds to cytoplasmic proteins and persists in the cell for up to 8 division cycles. Aims: To study the biodistribution of CFSE-labeled bone marrow MSCs after intravenous injection in rabbits Methods: Our experiment was performed with mature rabbits, not albinos, of both sexes, weighing 3000-4000 g. The source of MSC was a rabbits bone marrow. Cultivation was carried out in an atmosphere of 5% CO2 at a temperature of 37°C on αMEM medium (StemCells, Canada) containing platelet-rich plasma (4%), heparin (Russia, 2 U/mL), L-glutamine (StemCells, Canada, 2 mM). Cells were detached from plastic with 0.25% trypsin and stained with CFSE (Sigma, USA). The labeled cells were injected into the rabbit ear vein at an amount of (1,0-1,5)×106/kg. Animals were removed from the experiment through 1 (n=3) and 24 (n=3) hours after administration of allogeneic cells, and 24 hours (n=2) after the injection of autologous cells. The heart, lungs, liver, spleen, kidneys, and femurs were taken, followed by the histological preparations in the conventional way. After staining with 4’,6-diamidino-2-phenylindole, tissue sections were examined with an Axio Scope A1 luminescent microscope (×1000, excitation wavelength 475 nm, emission wavelength 530 nm). Count the number of labeled cells in the field of view. At least 10 fields per sample were evaluated. The results are presented as mean, minimum and maximum values. Results: At 1 hour after the allogeneic cells injection, the largest number of labeled MSCs in 1 field of view was detected in the bone marrow (1.7 (0-4)) and liver (1.2 (0-4)). Single luminescent cells were noted in the spleen (0.7 (0-2)) and lungs (0.4 (0-2)). There were no MSCs in the heart and kidneys. The mean number of labeled allogeneic MSCs in 1 field was 0.2 (0-3) in the kidney and 0.3 (0-1) in the bone marrow over a 24-hour period. Labeled cells were not found in the heart, lungs and spleen. Twenty-four hours after administration of autologously labeled MSCs, the mean number of luminescent cells in the bone marrow was 3.4 (0-9). Single CFSE+ cells were detected in liver (0.5 (0-2)), kidney (0.3 (0-2)) and lung (0.1 (0-1)). MSCs with specific green light were not found in the heart and spleen. Summary/Conclusion: The selective accumulation of CFSE+ MSCs in the bone marrow and liver 1 h after injection confirms their ability to homing. A decrease in the number of fluorescent allogeneic MSCs in the recipient’s body after 24 hours may be associated with immune rejection and indicates the absence of immune privilege of the studied cells. Labeled autologous MSCs remained in the accumulation organs after 24 h, which confirms the participation of histocompatibility antigens in the elimination of MSC from the organism. Keywords: Bone Marrow, Mesenchymal cells, Autologous, Allogeneic